/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package hivemall.tools.mapred;

import static hivemall.utils.hadoop.WritableUtils.val;
import hivemall.utils.hadoop.HadoopUtils;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDF;
import org.apache.hadoop.hive.ql.udf.UDFType;
import org.apache.hadoop.io.Text;

@Description(name = "rowid",
        value = "_FUNC_() - Returns a generated row id of a form {TASK_ID}-{SEQUENCE_NUMBER}")
@UDFType(deterministic = false, stateful = true)
public class RowIdUDF extends UDF {

    private long sequence;
    private int taskId;

    public RowIdUDF() {
        this.sequence = 0L;
        this.taskId = -1;
    }

    public Text evaluate() {
        if (taskId == -1) {
            this.taskId = HadoopUtils.getTaskId() + 1;
        }
        sequence++;
        String rowid = taskId + "-" + sequence;
        return val(rowid);
    }
}
